Additional Records and Extensions of Known Ranges of Mammals from Utah

In Short

This scientific paper updates the taxonomic and geographic record of Utah’s mammal populations, supplementing Stephen D. Durrant’s baseline 1952 monograph. Drawing on approximately 5,000 museum specimens gathered primarily by the University of Utah, the text documents range extensions, fills distributional gaps, and adds two previously unrecorded mammalian taxa to the state's fauna. Covering everything from high-altitude shrews to secretive bats, rodents, and large ungulates, it endures as a vital reference point for regional mammalogy, capturing a mid-century baseline of ecological documentation within the complex topography of the Great Basin and Colorado Plateau.

The Story

The work functions as an ongoing scientific accounting, taking up the precise boundaries where earlier state surveys left off. Beginning in the high alpine and canyon habitats, the text first considers the smallest insectivores and bats. Records of the dusky shrew and a direct visual observation of the water shrew in the Abajo Mountains extend the documented presence of these tiny mammals roughly eighty miles southward into San Juan County. Moving into nocturnal flying mammals, restudied specimens and new cave captures expand the known territories of several bats. Re-examination of a specimen from Uintah County reveals it to be the Yuma myotis rather than a little brown bat, moving its verified distribution 300 miles northeastward, while northern captures of the small-footed myotis, western pipistrelle, and long-eared bat establish that these species inhabit suitable microclimates statewide.

The focus then shifts across the state's varied terrains to examine ground squirrels, marmots, chipmunks, and pocket mice. Collecting efforts in the basin of ancient Pleistocene Lake Bonneville yield critical revisions. A yellow-bellied marmot specimen recovered from 10,000 feet on Deseret Peak in the Stansbury Mountains demonstrates that marmots crossed into the Bonneville basin, challenging earlier assumptions about their absence. Similarly, collections of Belding ground squirrels prove the species inhabits the Great Basin Drainage rather than remaining isolated within the Snake River system. In the east, Richardson ground squirrels are traced along the northern piedmont of the Uinta Mountains, while Uinta chipmunks are documented on the West Tavaputs Plateau, geographically isolated from eastern populations by the deep chasm of the Green River.

The central and southern plateaus reveal further complexity among small rodents. The Great Basin pocket mouse is formally added to the state's known fauna through extensive series collected from Washington, Garfield, and Wayne counties, showing subtle morphological intergradation between subspecies across the Aquarius Plateau. A single northern pocket gopher trapped in Summit County brings the state's total count of named pocket gophers to thirty-seven. Range extensions are likewise established for western harvest mice, grasshopper mice, red-backed mice, heather voles, meadow mice, and big jumping mice, establishing that many montane species inhabit continuous ranges along Utah's central mountain backbone.

The survey concludes by evaluating larger carnivores and ungulates. A gray fox skull from the Deep Creek Mountains extends its range 150 miles northward into western Utah. Two complete specimens of the rare river otter are recorded from the Raft River, preserved through state conservation agencies. Finally, the authors address big game: physical specimens confirm the southward movement of moose into Wasatch County, and a single young ram taken in the La Sal Mountains provides the state's very first complete scientific specimen of a native mountain sheep.

How It Unfolds

The insectivores and bats The examination opens with small mammals, using newly cataloged museum skins and close-range field sightings to push the boundary lines of shrews and bats dozens to hundreds of miles past their previously accepted borders.

The basin and plateau rodents The focus moves to sciurids and heteromyids, re-evaluating physical specimens from the Lake Bonneville basin and the Uinta Mountains to correct prior misidentifications and prove that several species cross major drainage divides.

The montane mice and voles Systematic trapping across high-altitude plateaus like Boulder Mountain and the Aquarius Plateau demonstrates that secretive voles, jumping mice, and pocket gophers occupy connected mountain ranges throughout central Utah.

The carnivores and large ungulates The study closes by documenting rare larger mammals, cataloging physical remains of gray foxes, river otters, expanding moose herds, and the first complete museum specimen of a mountain sheep from the La Sal Mountains.

The People

Stephen D. Durrant The primary authority on Utah's mammal fauna, Durrant works to refine, correct, and expand upon his own benchmark 1952 monograph. Seeking empirical precision, he scrutinizes skull measurements, pelage coloration, and geographical barriers to build a complete scientific catalog.

M. Raymond Lee A field researcher and co-author who contributes direct field observations and specimen collection. His decisive close-range observation of a water shrew swimming in North Creek provides the evidence needed to document an eighty-mile range extension.

Richard M. Hansen A co-author and field collector who gathers crucial specimens across eastern and northern Utah. His trapping efforts in Uintah and Daggett counties provide the physical proof required to establish northern range extensions for grasshopper mice and Richardson ground squirrels.

The Regional Game Officials and Collectors Field collectors, college professors, and state game employees—including James O. Lonnquist, Norman V. Chamberlain, and Fish and Game Director J. Perry Egan—who salvage rare specimens like otters, moose, and mountain sheep, transferring them to university collections for scientific study.

In Its Own Voice

"Study of this material discloses two kinds of mammals not heretofore known to occur in Utah, and extends the known limits of occurrence of many others..."

Context: The authors state the primary purpose of their paper in the opening paragraph, establishing it as an essential supplement to previous statewide taxonomic surveys.

"Usually we are extremely reluctant to record sight records, but do so in this instance because the water shrew is so distinctive that it can be readily recognized..."

Context: The text explains why a visual observation of a swimming shrew at North Creek was included despite rigid scientific standards requiring physical specimens.

"According to Harold Crane, of the Utah State Fish and Game Department, this ram was running with a herd of mule deer, and was the only mountain sheep that was seen."

Context: The authors describe the unusual circumstances surrounding the acquisition of the state's first complete museum specimen of a mountain sheep from the La Sal Mountains.

What It's Really About

At its core, the text is about the rigorous process of empirical scientific correction and the dynamic nature of biogeography. It demonstrates that animal ranges are not static lines on a map, but fluid biological boundaries dictated by mountain corridors, river chasms, and microhabitats. By comparing fresh physical specimens against historical literature, the authors illustrate how field collecting continually tests and refines theoretical ecological models. The work underscores the crucial role played by natural history collections, where preserved skulls, skins, and meticulous field notes serve as verifiable truth against assumptions, proving that even well-studied regions contain surprising ecological discoveries when examined with patience and taxonomic precision.

Why Read It Today

This paper appeals to field naturalists, mammalogists, biogeographers, and readers fascinated by the natural history of the American West. It reads not as a dramatic narrative, but as a dense, satisfying ledger of field discoveries, filled with specific elevations, mountain passes, canyon drainages, and precise geographic coordinates. It captures the texture of mid-century field biology—an era of deliberate trapping, careful skull measurements, and close coordination between state game wardens and university museums.

Readers should expect an uncompromisingly technical format: the text consists entirely of specialized scientific prose, subspecies nomenclature, measurement comparisons, and locality listings without narrative exposition. Yet beneath the dry scientific register lies a vivid portrait of Utah's wilderness landscapes. It evokes the quiet, hidden life of high-altitude plateaus, desert caves, and remote mountain streams, leaving the reader with a deep appreciation for the quiet discipline required to map the natural world item by item.